Electromagnetic friction device



'Sept' 27, 1932. A. P. WARNER 1,880,061

ELECTROMAGNETIC FRICTION DEVICE Original Filed Marchv, 1928 Patented Sept. 27, 1932 i 1,88* oiofL Y ogmai animation-tied Maren i vThis relates to friction, devices and `more particularly to: de?

vicesrfOlsuse'inelectric brakesand the like vhaving two annularxmagnetic elements,adaptei 1; editor axial gripping engagement. The :ap.

plicatioll, is `adivi'sion of my copendingapplil cationfSerial`No;,259,050, filed March 5,- 1928. Mgnetsoffthe lalbotge .character are capable nitudes[fory a vcomI)aratively small energizing currentprovided there. is no substantial=-lair gap'betfween the.: coacting armature andpolei faces. Particles of metal or other mateiriall wearing o l from the elements or coming onto y `rotatesand the vother"is.,relatively nonerotatable, fthe presence of such`fp-articles betweenQ the elements; producesa 'severe scori'ngor:`

rough'ening of the surfaces with airesultant decrease in the niagnets strengthand-ealsosan excessiveiand uneven :wearing atthecoacting-I are particularly-aggravated i friction de?,` vices wherein the coactlfng elements arefmain; tained in mechanical contactcontlnuously, mi

which case 4the; extraneous particles are held?` between the surfaces and continue Vtheir score:

ing action orlonger time-intervals. k'i

The primary object of/ thepresent inveneg tion is to overcome the difficulties aboVemen- -tioned Yby providing an electromagnetic Ifrici tion device having annular coacting leleineriigs cally .to remove extraneous' p'ai ti c :les'y from tween the elements andth'erbymaintai-n their `faces cleanandjsmootli.

Another obj'ec'tv'is to provide', 'in a friet device having annular friction elementsfar ranged for lrelative rotation,z la 'groov'edfsuif face on one ofthe elements for receiving-pare: ticles of extraneous material accumulating* betweentheelements and means for. main-? I tionfwilldbeconieapparentir-onfthefollowing f detailed;description-taken inconnectioni with the accompanying drawing, in which: 1

-l Eig.; 2 is. an elevational sli-owninEig. l'with the anchor plate of Vthe Ibwrake removed' andv Apart-'0f one magnetr element`v 1brokenaway;to show. the' face of .the

other :elementil i i nl While:the'inventioniis susceptible of various-modifications :and .alternative lconstruc-14 tions-l haveshown in the. drawing and will Lfherein .describe-'inll detail; thepreferred embodiment, but it :isi-to be .understood that I do not thereby intend' tolimit the-invention to the yspe'cic `t'ormE disclosed, but: intend to coverrall. Amodifications and falternative vconnl the* drawing the' Viav'eritili' is'" embio'aiea lfigure 1 isa verticalgsectional View of an electric brake. having- -a friction operatorf constructed inf :accordance r with the kpresent 1 invention-, the section i being; taken along the :structions allingwithin thespirit and scope :ofatlie invention aszexpressedrin the appended Y Y='clai-ms.' :21. 'Y surfaces. These ,obj ectionabl'e'characteristics 1 in; i anl electrically:controlledoperator of 'the l; so-calledl momentum type which is arrangedj `:to4 actuate a brake vfor :retardng the motion of a vehicle? wheel 4. :The-exemplary brake comprises a=drum .5 carried bythe wheel-andan expansibleibraking `means within the drum.l

:The brakingmeans is composed :of two' shoes y 6betweenwhosefadjacent ends "are 'cams-T mounted fforioscillation` -on anchorpins 8 K which are rigid with a non-rotatable-plate 9 and a'novel means which operates automatise*closing the open endof'fthe' drum.l i' Rigidfwith eac-h o am" 7 is 4Ta radially vdisposed crank arm f 10 whose 'inner end 'is' enga'ge'ablel with the short ai'infof l`abll crank'lev'er'll mounted on a hub thefplate'i) for oscillation taining the elements in flight'inechanical con'- -lhalmg' QPF-@96- at. ffice? .0f l'latlvly I lra tact=while they' are"deenergized` so as to -ren-' TQWmlml Wldth" The rm'glsf CODSPIUES der the grooves osaid surface 'continuou'sly74 magnefl armature and'prferably vl'S rotatoperative to produce a'cjleaning'actionf, jablewith-the'drums' Inthef'vpresent-instance 5 9 Other objects and advantages of the invenit is disposedexternally of the drum and iS 10o in the form of a thin flange inte al with the drum near. the inner edge of the atter.

The ring 14 constitutesthe magnet proper and is of U-shaped cross-section carrying an annular winding 15 between two concentric poles 16 whose faces are disposed in a common plane and coact with the inwardly facing surface of the armature ring thereby forming a substantially closed flux circuit around the winding 15. The magnet poles are separated by plates 17 of non-magnetic and wear-resisting material whose surfaces are flush with the pole faces. 'The magnet is rigid with two long radial arms 18 of the bell crank 11.

A plurality of leaf springs 19 on the plate 9 bear against the magnet ring and urge the ring and bell crank continuously toward the face of the armature 13 while the winding 15 is deenergized. This yieldableV floating mounting of the magnet allows for the inherent lateral wobblingof the armature ring during rotation of the vehicle wheel and maintains the friction faces of the rings in intimate mechanical contact,' thereby tending lto eliminate any air gap which such lateral wobbling would otherwise produce. A spring 2O of the hairpin type, acting between a stop 21` on the plate 9 and a lug 22 on one of the arms 18, normally overcomes the tendlency ofthe magnet ring to move by reason of its constant contact with the armature. Thus the magnet is maintained in a normal brake-released position (Fig. 2) so long -as the winding 15 is deenergized.

Upon the application of energizing cur` rent to the winding '15 when the wheel is rotating, the two rings 13 and 14 are drawn into powerful gripping engagement, themagnet ring being carried along frictionally with the armature with the result that the bell crank 11 actua-tes the cranks 10 which expands the brake shoes against the drum. After the normal clearance between 'the shoes and the drum has been taken up, slippage occurs between the rings and the brake remains set until the winding 15 is deenergized.' When the latter occurs, the magnet 1s returned to released position by the spring 20 and the pressure on the brake shoes 1s thereby relieved.

In order to prevent particles of metal or. other extraneous material frombeing retained on the .friction faces on the ma etic Iwings, thereby causing. a detrimental air gap to exist between them, means is provided `which acts automatically in the .rotation of thevehicle wheel to quickly remove anyv particles y that may accumulate between the rings. This means comprises one or more transverse depressions or grooves 23 cut, stamped or otherwise suitably formed in the friction face of one' or both of the magnetic rings so that the particles will, due to the relative motion between the engaging surrotation of the vehicle wheel.

faces be brou ht opposite one of the grooves and become e osited therein. Whlle the width and dept of the grooves need only be suiiicient to receive the largest particles which are apt to accumulate, it is preferred to make them substantially wider and deeper so as to allow the particles to move through the grooves freely by a centrifugal. action thereby avoiding clogging of the grooves.

The centrifugal force for excluding the particles from the grooves is induced by For this reason the grooves are preferably formed in the face of the armature ring and extend 1minterruptedly across the entire face of the ring. The centrifugal action is most effective when the grooves are disposed' substantially radially, which position is also preferred because the decrease of the magnet strength by ally prevented when more than one groove is employed. In the present instance there are six grooves spaced equidistant around the armature ring.

With the grooves arranged as above described, it will be apparent that any parti cles of extraneous material coming between the magnetic elements during the light engagement due to the springs 19 or to the powerful engagement causedby energization of the winding 15, will be presented quickly to one of the grooves 23 and immediately thrown out by centrifugal action. Scoring and excessive wearing of the friction Vsurfaces is thereby effectually prevented; It will be observed that any particles existing between the rings when the magnet is energized will produce a greater scoring action than when the magnet is deenergized. Thus, it is de? sirable that all of the particles-be removed from the friction faces at the time when the winding is energized so as to avoid entrap- `ment of the particles when they are under a powerful gripping pressure. Thisresult is accomplished in the present instance by coordination of the springs 19 and the grooves scoring by extraneous particles.

I claim as my invention:

1. In an electromagnetic friction device, jthe combination of a normally rotatable magnetic ring having a substantially fiat friction surface disposed in a plane perpendicular to its rotational axis, a' relatively non- .rotatable magnetic ring having a friction surface opposing and coacting with said first nientioned surface, and a magnetic winding carried by one of said rings and adapted when energized to cause gripping engagement of said surfaces, said rotatable ring having a plurality of grooves formed in its friction surface at annularly spaced points and extending transversely of and entirely across said surface so as to receive particles of material accumulatingbetween said surfaces and to throw such particles oif from the rotating ring by centrifugal action.

2. In an electromagnetic friction device, the combination of a rotatable ring composed of magnetic material and having a flat radiall;7 disposed friction face, a second ring having a cooperatingface, a winding carried by one of said rings adapted when energized to bring said faces into gripping engagement, and a groove formed in and extending transversely of the face of said rotatable ring for collecting particles of extraneous material and thereby removing said particles from the faces of said rings, said groove having an outwardly opening end from which extraneous particles deposited in said groove will be excluded by centrifugal action.

3. In an electromagnetic friction device, the combination of a rotatable ring composed of magnetic material and having a substantially flat and radially disposed friction face, a second ring of magnetic material having a fiatface engageable with said rst mentioned face, a magnetic winding on one of said rings adapted when energized to cause gripping engagement between said faces, means for removing particles of extraneous material from said faces comprising a depression in one of said faces for collecting such particles in the relative rotation between the rings, and means acting constantly to maintain the faces of said rings in light mechanical contact and thereby render said particle removing means operative while said winding remains deenergized.

In testimony whereof, I have hereunto affixed my signature.

ARTHUR P. WARNER. 

